A valve timing controller is conventionally known for changing a relative rotational phase between two rotating elements that rotate in association with a drive shaft and a camshaft, respectively. For example, JP-2005-48707A discloses a valve timing controller equipped with arm members for linking a first rotating element (a sprocket) with a second rotating element (an output shaft) via a revolute pair. The valve timing controller also includes a phase changing mechanism for changing a relative rotating phase between the first rotating element and the second rotating element. Furthermore, the valve timing controller includes an electric motor for producing rotating torque for a motion of the revolute pair. In addition, the valve timing controller includes a motion converting mechanism for transmitting the rotating torque by the electric motor to the arm members.
The electric motor, the motion converting mechanism, and the phase changing mechanism are axially combined. The motion converting mechanism and the phase changing mechanism are configured in such a manner as to be accommodated in the sprocket.
In addition, the motion converting mechanism is equipped with a gear part including a ring gear and a planetary gear. The planetary gear performs a planetary motion by engaging with the ring gear. The motion converting mechanism also includes a guide member for guiding a movable member, which supports the revolute pair of the arm members around an axis as a controlling object. An engagement projection projecting from the planetary gear is supported by an engagement bore located in the opposite side of the arm members of the guide member. Also, the movable member slides relatively along a guide passage formed in the guide member, thus converting a rotational motion of the motor into a predetermined revolute pair motion of the movable member.
In the conventional technology, the ring gear and the planetary gear engage with each other by several teeth, producing a cantilever state thereof, and therefore there is a possible decline thereof toward a thrust direction. For example, when the decline in the thrust direction occurs, the planetary gear swings in the thrust direction within a thrust gap, and undesirable sound can be result, such as a slapping sound.
Therefore, reduction of the thrust gap is suggested. However, this idea is designed to axially combine a gear part with another member, such as a link mechanism formed of arm members constituting a revolute pair. Accordingly, this idea requires a precision improvement of each member in order to reduce variation of the thrust gap of each member.